This invention relates generally to laser amplifiers and, more particularly, to end-pumped zig-zag solid state lasers. A zig-zag solid state laser includes an elongated slab of rare earth doped lasing material, such as yttrium-aluminum-garnet (YAG). An input beam generated by a master oscillator is launched into one end facet of the slab, at an angle selected to result in multiple internal reflections from the internal faces of the slab. A pump beam is also input at one end of the slab and amplification of the input beam takes place as the input beam is reflected back and forth along the slab. The doped region of the slab in which amplification takes place is cooled by external means.
The laser structure briefly described above is disclosed in detail in U.S. Pat. No. 6,094,297, referred to in this document as the Injeyan '297 patent, issued to Hagop Injeyan et al. and assigned to the same assignee as the present invention.
Although the amplifier described in the Injeyan '297 patent is efficient and produces a beam of good quality and polarization properties, improvement is called for when many such amplifiers are combined to produce higher power beams. For such a configuration, it is highly desirable that each amplifier output should have linear polarization. Linear polarization is also required by applications that utilize frequency conversion of the output. As this zig-zag slab architecture has been extended to higher powers, it has been found that the polarization properties of the amplified output can degrade significantly, such that linear polarization can no longer be maintained effectively.
Accordingly, there is a need for an improved zig-zag slab laser amplifier having significantly improved linear output polarization properties. The present invention is directed to this end.